There are 2 repositories under leaked-code topic.
ROBLOX + ROBLOX STUDIO PC & Mobile (ANDROID and IOS) leaked source code, from 2016. Untouched code.
The source to a imageboard by the name of 4chan that suffered a brutal fate to the altchan "soyjak.party". This will NOT run on anything newer than PHP 5.0.
Leaked AntiPhishingDemo source code.
Scan thousands git repositories for leaked secrets
Source code for Quantic Dream's in-house engine. This copy is combined from copies dated from April and July of 2006.